Modelling of swelling of PVA hydrogels considering non-ideal mixing behaviour of PVA and water

Non-ideal mixing behaviour between Pluronics and pre-formed 16-3-16/plasmid DNA complexes depends on solution composition but primarily poly(propylene oxide) block length.

Download Full-text

Non-Ideal Mixing Behaviour of Hydrogen Bonding in Mixtures of Protic Ionic Liquids

ChemPhysChem ◽

10.1002/cphc.201402760 ◽

2014 ◽

Vol 16 (2) ◽

pp. 299-304 ◽

Cited By ~ 39

Author(s):

Koichi Fumino ◽

Anne-Marie Bonsa ◽

Benjamin Golub ◽

Dietmar Paschek ◽

Ralf Ludwig

Keyword(s):

Hydrogen Bonding ◽

Ionic Liquids ◽

Protic Ionic Liquids ◽

Ideal Mixing ◽

Mixing Behaviour

Download Full-text

The Thermooxidation and Resistance to Moulds Action of Some Polyethylene Sorts Used at Anticorrosive Insulation of the Underground Pipelines

Materiale Plastice ◽

10.37358/mp.17.3.4869 ◽

2017 ◽

Vol 54 (3) ◽

pp. 447-452 ◽

Cited By ~ 1

Author(s):

Adriana Mariana Bors ◽

Nicoleta Butoi ◽

Alina Ruxandra Caramitu ◽

Virgil Marinescu ◽

Iosif Lingvay

Keyword(s):

Heat Treatment ◽

Thermal Analysis ◽

Culture Media ◽

Power Cables ◽

Polymerization Degree ◽

Crosslinking Degree ◽

Underground Pipelines ◽

Predominant Process ◽

Underground Power Cables ◽

Coupled Techniques

Polyethylene (PE) insulations have a wide applicability in the insulation of both underground pipelines and underground power cables. In this context, by coupled techniques of thermal analysis (TG/DTG+DTA) and microbiological determinations, have been studied thermooxidability and resistance to moulds action of some polyethylene sorts. Following the processing of the experimental data obtained by thermal analysis it was found that during the applied heat treatment (100 grd C), in the first approx. 380 h, there is a growth of LDPE (low density polyethylene) polymerization degree by elongation of the aliphatic chains, after which the predominant process consists in the structure crosslinking. For MDPE (mean density polyethylene) samples, during the thermal treatment applied, it was found that the crosslinking degree of polyethylene (PE) increased without significant molecular weight change (with all the related consequences of increasing the weight of the tertiary and quaternary carbon atoms in the molecule). Microbiological determinations have highlighted that the resistance to filamentous fungal action of LPDE is higher than that of the investigated MDPE. It was found that after heat treatment applied (1000 h and 100 oC), both at LDPE and at MDPE, decreases the resistance to moulds action is decreased. It has also been found that moulds action resistance is substantially decreased when inoculated culture media and PE samples are exposed to an alternative electric field of 50 Hz - 6 Vrms/cm.

Download Full-text

First and second laws of thermodynamics: relationship, “inconsistency”, hidden effects

Voprosy Materialovedeniya ◽

10.22349/1994-6716-2020-101-1-63-73 ◽

2020 ◽

pp. 63-73

Author(s):

A. M. Savchenko ◽

Yu. V. Konovalov ◽

A. V. Laushkin

Keyword(s):

Free Energy ◽

Internal Energy ◽

Second Law Of Thermodynamics ◽

Second Law ◽

Entropy Of Mixing ◽

Ideal Mixing ◽

Laws Of Thermodynamics ◽

Relationship Of ◽

The Relationship

The relationship of the first and second laws of thermodynamics based on their energy nature is considered. It is noted that the processes described by the second law of thermodynamics often take place hidden within the system, which makes it difficult to detect them. Nevertheless, even with ideal mixing, an increase in the internal energy of the system occurs, numerically equal to an increase in free energy. The largest contribution to the change in the value of free energy is made by the entropy of mixing, which has energy significance. The entropy of mixing can do the job, which is confirmed in particular by osmotic processes.

Download Full-text

Water-Tree Resistant Characteristics of Crosslinker-Modified-SiO2/XLPE Nanocomposites

Materials ◽

10.3390/ma14061398 ◽

2021 ◽

Vol 14 (6) ◽

pp. 1398

Author(s):

Yong-Qi Zhang ◽

Xuan Wang ◽

Ping-Lan Yu ◽

Wei-Feng Sun

Keyword(s):

Electric Fields ◽

Tree Growth ◽

Mechanical Analysis ◽

Water Molecules ◽

Crosslinking Degree ◽

Water Tree ◽

Tree Resistance ◽

Alternating Electric Fields ◽

Trimethylolpropane Triacrylate ◽

Mechanical Performances

Trimethylolpropane triacrylate (TMPTA) as a photoactive crosslinker is grafted onto hydrophobic nanosilica surface through click chemical reactions of mercapto double bonds to prepare the functionalized nanoparticles (TMPTA-s-SiO2), which are used to develop TMPTA-s-SiO2/XLPE nanocomposites with improvements in mechanical strength and electrical resistance. The expedited aging experiments of water-tree growth are performed with a water-knife electrode and analyzed in consistence with the mechanical performances evaluated by means of dynamic thermo-mechanical analysis (DMA) and tensile stress–strain characteristics. Due to the dense cross-linking network of polyethylene molecular chains formed on the TMPTA-modified surfaces of SiO2 nanofillers, TMPTA-s-SiO2 nanofillers are chemically introduced into XLPE matrix to acquire higher crosslinking degree and connection strength in the amorphous regions between polyethylene lamellae, accounting for the higher water-tree resistance and ameliorated mechanical performances, compared with pure XLPE and neat-SiO2/XLPE nanocomposite. Hydrophilic TMPTA molecules grafted on the nano-SiO2 surface can inhibit the condensation of water molecules into water micro-beads at insulation defects, thus attenuating the damage of water micro-beads to polyethylene configurations under alternating electric fields and thus restricting water-tree growth in amorphous regions. The intensified interfaces between TMPTA-s-SiO2 nanofillers and XLPE matrix limit the segment motions of polyethylene molecular chains and resist the diffusion of water molecules in XLPE amorphous regions, which further contributes to the excellent water-tree resistance of TMPTA-s-SiO2/XLPE nanocomposites.

Download Full-text

Insights into the Microstructural Evolution Occurring during Pyrolysis of Metal-Modified Ceramers Studied through Selective SiO2 Removal

Materials ◽

10.3390/ma14123276 ◽

2021 ◽

Vol 14 (12) ◽

pp. 3276

Author(s):

Aitana Tamayo ◽

Juan Rubio ◽

Fausto Rubio ◽

Mᵃ Angeles Rodriguez

Keyword(s):

Structural Characteristics ◽

Domain Size ◽

Ceramic Composites ◽

Silicon Oxycarbide ◽

Crosslinking Degree ◽

Molecular Precursors ◽

Textural Characterization ◽

Polymer Derived Ceramic ◽

Ultimate Properties ◽

Lower Carbon

Silicon oxycarbide ceramers containing 5% aluminum, zirconium, and cobalt with respect to the total Si amount are prepared from a commercial polysiloxane and molecular precursors and pyrolyzed at temperatures ranging from 500 to 1000 °C. HF etching is carried out to partially digest the silica phase, thus revealing structural characteristics of the materials, which depend upon the incorporated heteroatom. From the structural and textural characterization, it was deduced that when Al enters into the ceramer structure, the crosslinking degree is increased, leading to lower carbon domain size and carbon incorporation as well. On the contrary, the substitution by Zr induced a phase-separated SiO2-ZrO2 network with some degree of mesoporosity even at high pyrolysis temperatures. Co, however, forms small carbidic crystallites, which strongly modifies the carbonaceous phase in such a way that even when it is added in a small amount and in combination with other heteroatoms, this transient metal dominates the structural characteristics of the ceramer material. This systematic study of the ceramer compounds allows the identification of the ultimate properties of the polymer-derived ceramic composites.

Download Full-text

The Influence of Filler Size and Crosslinking Degree of Polymers on Mullins Effect in Filled NR/BR Composites

Polymers ◽

10.3390/polym13142284 ◽

2021 ◽

Vol 13 (14) ◽

pp. 2284

Author(s):

Miaomiao Qian ◽

Bo Zou ◽

Zhixiao Chen ◽

Weimin Huang ◽

Xiaofeng Wang ◽

...

Keyword(s):

Particle Size ◽

Strain Energy ◽

Mathematical Expression ◽

Rubber Matrix ◽

Mullins Effect ◽

Butadiene Rubber ◽

Crosslinking Degree ◽

Test Range ◽

Two Factors ◽

The Matrix

Two factors, the crosslinking degree of the matrix (ν) and the size of the filler (Sz), have significant impact on the Mullins effect of filled elastomers. Herein, the result. of the two factors on Mullins effect is systematically investigated by adjusting the crosslinking degree of the matrix via adding maleic anhydride into a rubber matrix and controlling the particle size of the filler via ball milling. The dissipation ratios (the ratio of energy dissipation to input strain energy) of different filled natural rubber/butadiene rubber (NR/BR) elastomer composites are evaluated as a function of the maximum strain in cyclic loading (εm). The dissipation ratios show a linear relationship with the increase of εm within the test range, and they depend on the composite composition (ν and Sz). With the increase of ν, the dissipation ratios decrease with similar slope, and this is compared with the dissipation ratios increase which more steeply with the increase in Sz. This is further confirmed through a simulation that composites with larger particle size show a higher strain energy density when the strain level increases from 25% to 35%. The characteristic dependence of the dissipation ratios on ν and Sz is expected to reflect the Mullins effect with mathematical expression to improve engineering performance or prevent failure of rubber products.

Download Full-text

The High Pressure Rheology of Mixtures

Journal of Tribology ◽

10.1115/1.1760552 ◽

2004 ◽

Vol 126 (4) ◽

pp. 697-702 ◽

Cited By ~ 9

Author(s):

Scott Bair

Keyword(s):

Molecular Weight ◽

High Pressure ◽

Binary Systems ◽

Viscosity Coefficient ◽

Shear Thinning ◽

Newtonian Viscosity ◽

Double Shear ◽

Ideal Mixing ◽

Viscosity Behavior ◽

Single Flow

The Newtonian mixing rules for several binary systems have been experimentally investigated. Some systems show non-ideal mixing response and for some systems the non-ideal response is pressure-dependent, yielding an opportunity for manipulation of the pressure-viscosity behavior to advantage. The mixing of differing molecular weight “straight cuts” can produce very different pressure-viscosity response. This behavior underscores the difficulty in predicting the pressure-viscosity coefficient based upon chemical structure and ambient viscosity since the molecular weight distribution is also important, but it also provides another opportunity to control the high-pressure response by blending. The first experimental observation of double shear-thinning within a single flow curve is reported. Blending then provides the capability of adjusting not only the Newtonian viscosity but also the non-Newtonian shear-thinning response as well.

Download Full-text